Fix few duplicate word occurrences (#11381)

(cherry picked from commit cb4b9be458)

src/libstore/local-overlay-store.md

@@ -77,13 +77,13 @@ The parts of a local overlay store are as follows:
 
     The lower store directory and upper layer directory are combined via OverlayFS to create this directory.
     Nix doesn't do this itself, because it typically wouldn't have the permissions to do so, so it is the responsibility of the user to set this up first.
-    Nix can, however, optionally check that that the OverlayFS mount settings appear as expected, matching Nix's own settings.
+    Nix can, however, optionally check that the OverlayFS mount settings appear as expected, matching Nix's own settings.
 
   - **Upper SQLite database**:
 
     > Not directly specified.
     > The location of the database instead depends on the [`state`](#store-experimental-local-overlay-store-state) setting.
-    > It is is always `${state}/db`.
+    > It is always `${state}/db`.
 
     This contains the metadata of all of the upper layer [store objects][store object] (everything beyond their file system objects), and also duplicate copies of some lower layer store object's metadta.
     The duplication is so the metadata for the [closure](@docroot@/glossary.md#gloss-closure) of upper layer [store objects][store object] can be found entirely within the upper layer.

src/nix/flake.md

@@ -120,7 +120,7 @@ Contrary to URL-like references, path-like flake references can contain arbitrar
 
 ### Examples
 
-* `.`: The flake to which the current directory belongs to.
+* `.`: The flake to which the current directory belongs.
 * `/home/alice/src/patchelf`: A flake in some other directory.
 * `./../sub directory/with Ûñî©ôδ€`: A flake in another relative directory that
   has Unicode characters in its name.